Recently, the internal circuits of an integrated circuit (IC) chip have been laid out more and more compactly. Consequently, the chip generates higher and higher heat. When a personal computer works, the compact IC chip such as CPU or graphics chip will generate high heat. In order to keep the IC chip functioning lastingly, it is necessary to maintain the IC chip at an optimal working temperature. In this case, the efficiency of the IC chip will not deteriorate due to rise of temperature and the IC chip is protected from damage. In general, a heat dissipation device is used to directly contact the surface of the electronic component for dissipating the heat generated by the electronic component. Accordingly, it can be ensured that the electronic component works normally with a longer lifetime.
A cooling fan is an inevitable component of a heat dissipation device. The cooling fan serves to quickly carry away the heat from the radiating fin assembly by way of convection.
However, after a long period of operation, the cooling fan itself will generate heat, which may cause malfunction of the cooling fan or even damage of the cooling fan. Therefore, some manufacturers have tried to improve the conventional cooling fans so as to overcome the above problem.
FIGS. 1A and 1B show a conventional cooling fan, which includes a fan propeller 10, a shaft seat mount 13 and a heat dissipation board 15. The shaft seat mount 13 is made of plastic material, including a shaft bushing 131, a base section 132 and multiple fixing arms 133. The fan propeller 10 is rotatably connected with the shaft bushing 131 and has an internal receiving space 1311 for accommodating the shaft 101 of the fan propeller 10. The base section 132 radially extends from the circumference of the bottom end of the shaft bushing 131. First ends of the fixing arms 133 extend from the circumference of the base section 132 in a direction away from the shaft bushing 131. Second ends of the fixing arms 133 are formed with fixing holes 1331. Screws 16 can be passed through the fixing holes 1331 to lock the shaft seat mount 13 with the heat dissipation board 15. An upper face of the heat dissipation board 15 is formed with one or more locking holes 151 in alignment with the fixing holes 1331 of the fixing arms 133 respectively. The screws 16 are respectively passed through the fixing holes 1331 and screwed into the locking holes 151 to securely lock the shaft seat mount 13 on the heat dissipation board 15 with the upper face of the heat dissipation board 15 in contact with a lower face of the shaft seat mount 13.
After a long period of high-speed operation, the fan propeller 10 and the shaft 101 thereof will generate heat, which is spread over the receiving space 1311 of the shaft bushing 131. At this time, the shaft bushing 131 will absorb the heat and slowly conduct the heat to the base section 132. The base section 132 then conducts the heat to the heat dissipation board 15. Accordingly, only the part of the upper face of the heat dissipation board 15 that is not in contact with the shaft seat mount 13 can dissipate the heat. As a result, the heat dissipation area is limited and the heat dissipation effect is poor.
There is another problem existing in the conventional cooling fan. That is, when assembling the cooling fan, the shaft seat mount 13 is placed on the heat dissipation board 15. An operator uses a screwdriver (not shown) to screw the screws 16 into the fixing holes 1331 of the fixing arms 133 and the locking holes 151 of the heat dissipation board 15. After the shaft seat mount 13 is fixed on the heat dissipation board 15. Then the operator applies force onto the fan propeller 10 to move the fan propeller 10 into the receiving space 1311 of the shaft bushing 131, whereby the shaft 101 of the fan propeller is inserted into the receiving space 1311 and connected with the shaft bushing 131. It often takes place that an operator over-force the screws 16 to deform the shaft seat mount 13 and thus affect the verticality of the shaft bushing 131. On the other hand, an operator may under-force the screws 16. Under such circumstance, the screws 16 are apt to loosen to unlock the shaft seat mount 13 or even cause damage of the cooling fan in case the fan propeller 10 detaches from the shaft seat mount 13 and the heat dissipation board 15 in operation. Therefore, it is hard to control the magnitude of the applied force in the assembling process so that the uniformity of the products is poor. In addition, the labor cost and manufacturing cost are increased.
According to the above, the conventional cooling fan has the following defects:    1.The heat dissipation efficiency is poor.    2.The labor cost is increased.    3.The manufacturing cost is increased.    4.The heat dissipation area is limited.    5.The uniformity of the products is poor.